Presently known telephone plugs usually comprise an insulation housing including a plurality of contacts, the housing accommodating an electrical cable that includes an outer jacket and a number of individual conductor wires which terminate at the contacts. Each such conductor wire includes an individual conductor having its own surrounding insulation. Such wires are hereinafter referred to as "conductors". The contacts of the telephone plug pierce the surrounding insulation of respective wires to contact the conductors. For ease of notation, such a connection is hereinafter described as the contacts piercing the conductors.
When the conductors of the cable are provided as twisted pairs, in order to properly terminate each of the individual conductors of the cable it is necessary to untwist the twisted conductor pairs. Such untwisting results in a highly undesirable effect, known in the art as Near End Crosstalk (NEXT) resulting in signal disturbances at the connector.
Connectors are generally classified as having transmission speeds defined by category, with connectors operating at transmission speeds in category 3 (hereinafter Category 3connectors) having transmission characteristics specified up to 16 MHz, Category 4 connectors having transmission characteristics specified up to 20 MHz, and Category 5 connectors having transmission characteristics specified up to 100 MHz. The high frequencies at which category 5 (and higher) connectors operate result in potentially significant crosstalk, and require specific measures to be taken to meet NEXT loss standards.
NEXT loss is a measure of signal coupling from one circuit to another within a connector. NEXT loss is derived from swept frequency voltage measurements on short lengths of 100 .OMEGA. twisted-pair test leads terminated to the connector under test. In such measurements, a balanced input signal is applied to a disturbing pair of the connector while the induced signal on the disturbed pair is measured at the near-end of the test leads. In accordance with Telecommunications standard TSB40-A of the Telecommunication Industry Association/Electronic Industry Association (TIA/EIA) published in the Telecommunications Systems Bulletin, NEXT loss at any frequency f is required to meet the following limitation: EQU NEXT(f).gtoreq.NEXT(16)-20 log(f/16),
where NEXT(16) is the minimum NEXT loss at 16 MHz, f is frequency in MHz in the range from 1 MHz to the highest referenced frequency, and NEXT(f) is the performance at that frequency.
To determine NEXT loss requirements for connectors of different Categories at a given frequency, the value used for NEXT(16) is 34 dB for a category 3 connector, 46 dB for a category 4 connector and 56 dB for category 5 connector.
Additionally, the above described standard establishes requirements on Return Loss, which is a measure of the degree of impedance matching between the cable and connector, derived from swept frequency voltage measurements on short lengths of 100 .OMEGA. twisted-pair test leads before and after inserting the connector under test. More specifically, it is required that, for category 4 and 5 connectors, the minimum return loss shall be 23 dB or greater for frequencies between 1 and 20 MHz. For frequencies from 20 to 100 MHz, category 5 connectors shall exhibit a minimum return loss of 14 dB or greater These return loss values are chosen to limit peak reflected voltage of 7% or less up to 20 MHz, and to 20% or less from 20 to 100 MHz.
According to the above described requirements of (TIA/EIA), the connecting hardware used for 100 UTP (Unshielded Twisted Pair) cabling shall be installed to provide minimum signal impairment by preserving wire pair twists as closely as possible to the point of mechanical termination. The amount of untwisting in a pair as a result of termination to connecting hardware shall be no greater than 13 mm (0.5 in) for category 5 cables, and no greater than 25 mm (1.0 in) for category 4 cables. This requirement is imposed to minimize untwisting of wire pair and the separation of conductors within a pair.
An additional cable management practice that should be observed to reduce untwisting of pairs is to strip back only as much cable jacket as is required to terminate on connecting hardware.
It is known that many professionals have mistakenly specified the above noted 13 mm standard as a requirement for UTP cable jacket removal. However, the available configurations of connector hardware termination structures does not permit significant reductions of untwisted pair length below the 13 mm maximum.
It is thus an object of the present invention to provide a termination structure for a telephone connector which allows reduction of the amount of wire that is untwisted for termination below the 13 mm maximum value, to lengths as short as slightly more than 2.5 mm, and thus to provide significant reduction in the near end crosstalk experienced at the connector even for data transmission rates of 100 MHz and greater.
It is a more specific object of the invention to provide a termination structure requiring a length of untwisted wire which is approximately 5 mm, thus to permit the structure to be used in Category 3, Category 4, Category 5, and higher Categories as defined in the industry.
It is yet another object of the invention to provide a termination structure having a first region which has internal dimensions that are sufficiently large to acccept a jacketed cable therein and extending to within a short distance of contacts for the conductors, a second region having smaller internal dimensions than the first region for receiving therein the unjacketed cable conductors and extending only the short distance between the end of the jacketed cable and the contacts, and a short, rigid sleeve fitting within the short distance of the second region and accepting a short length of the untwisted conductor wires to enable positioning of such a short length of wire for making electrical contact with external contacts therefor.
It is a more specific object of the invention to provide such a structure wherein the short length of untwisted conductor wires is less than 13 mm.
It is still a more specific object of the invention to provide such a structure wherein the short length of untwisted conductor wires is in a range of 3 to 8 mm.
Still a more specific object of the invention is to provide a terminating structure wherein the short length of the untwisted conductor wires is approximately 5 mm.
It is yet another object of the invention to provide a terminating structure wherein the short distance of the second region and of the sleeve is less than 13 mm.
It is still another object of the invention to provide a terminating structure wherein the short distance of the second region and of the sleeve is in a range of 3 to 8 mm.
It is still another object of the invention to provide a terminating structure wherein the short distance of the second region and of the sleeve is approximately 5 mm.
It is a further object of the invention to provide a Category 5 connector having a terminating structure which accepts untwisted conductor pairs of a jacketed cable having a length of approximately 5 mm, thus to reduce or eliminate Near End Crosstalk (NEXT) therebetween when data is transferred at a frequency of 100 MHz and greater.
It is yet a more specific object of the invention to provide a terminating structure for a telephone connector having a first region for receiving a portion of jacketed cable, and only a single region with substantially a parallelopiped shape for receiving therein unjacketed cable conductors and a short, rigid sleeve having a shape which is substantially a parallelopiped, the sleeve being substantially fully enclosed in the single region and accepting a short length of untwisted conductor wires for making electrical contact with external contacts therefor.
It is still another object of the invention to provide a terminating structure for a category 5 telephone connector which includes a short region having a substantially parellelopiped shape for fully receiving therein a short sleeve, having a substantially parallelopiped shape and guiding a short portion of conductor wires to external contacts therefor, while retaining a larger region for receiving a section of the jacketed cable and including a strain relief for the cable in the larger region.